Fix code P0133 trouble code

A P0133 trouble code Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 1) to changes in fuel delivery. This sensor is located on the engine bank that houses #1 cylinder and is located BEFORE the catalytic converter

The PCM sends a reference voltage (usually 5-volts) to the variable resistor in the oxygen sensor and looks for a return voltage. It expects to see a rapidly changing return voltage varying from .1-volts to .95-volts. If the voltage doesn’t switch rapidly, the PCM will set a trouble code P0133.

What causes a P0133 trouble code?

Thee computer sets this code once the engine is in closed looop for at least 60-seconds, the coolant is up to operating temperature and the engine is running at 1,000-3,000 RPM. The computer is looking at the amount of time the oxygen sensor takes to switch between a rich and lean reading. If the time is longer than 0.114 seconds, the P0133 trouble code is set.

How to fix a P0133 trouble code?

Auto parts store clerks will tell you to change the oxygen sensor. That’s bad advice. While the sensor itself can be worn to the point where it’s “Lazy” worn sensor or contaminated, you should start your diagnostics by checking these other items that can cause a P0133 trouble code.

What to check for a P0133 trouble code BEFORE you replace the sensor?

Keep in mind that this code is telling the computer that it’s not responding

Manifold Absolute Pressure Sensor

quickly enough. So the problem can be the sensor itself of an exhaust mixture that isn’t changing rapidly enough. For example: a leaking fuel injector and saturate the exhaust and prevent the oxygen sensor from seeing a rapid change.

Fuel Injector

A leaking fuel pressure regulator could cause the same condition. And, a bad MAP sensor that reporting the wrong engine vacuum can cause this. Check out all of those before replacing the oxygen sensor.

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